JPS6422668A - Hydraulic pressure boosting device - Google Patents

Abstract

PURPOSE:To carry out stable valve operation by forming a reservoir side discharge passage in the center section of a selector valve which is arranged in a brake booster piston and is urged toward an input member by a spring, and by providing a throttle device upstream of an output so as to decrease the differential pressure across the selector valve. CONSTITUTION:Hydraulic pressure is fed from a pump 54 into a supply valve section 200 and a discharge valve seciton 300 of a selector valve 80 which is disposed in a booster piston 40 integrally incorporated with a primary piston 14 in a master cylinder 12 and urged toward an input member (pedal rod) 100 by means of a spring 82, and is then led into pressure chambers 88a through 88c from the supply valve section 200 so as to obtain a predetermined boost pressure. After operation of pressure boosting, the hydraulic pressure is fed from the discharge valve section 300 to a discharge passage 120 in the center part of the selector valve. A throttle device 400 is provided between the discharge passage 120 and an outlet port 48 so as to decrease the pressure differential across the selector valve 80. Thereby it is possible to prevent unstable operation of the selector valve which is caused by a differential pressure generated upon abrupt discharge.